WO2016038280A1

WO2016038280A1 - Vane with spoiler

Info

Publication number: WO2016038280A1
Application number: PCT/FR2015/052326
Authority: WO
Inventors: Laurent Jablonski; Pierre-Guillaume BARDIN; Philippe Gérard Edmond JOLY
Original assignee: Snecma
Priority date: 2014-09-08
Filing date: 2015-09-03
Publication date: 2016-03-17
Also published as: RU2701677C2; FR3025553B1; FR3025553A1; CN106852162A; CA2960089A1; RU2017107567A3; US10598033B2; US20170298750A1; JP2017532484A; BR112017004472B1; CN106852162B; RU2017107567A; EP3191688A1; CA2960089C; JP6869174B2; BR112017004472A2

Abstract

The invention relates to a vane for a turbine engine. The vane (12') has a blade (13') and a root (18') to be inserted into an axial groove of a turbine engine disc. The upstream end (450') of the root is connected to a radially inner end (430') of the leading edge (431') of the blade by the upstream end of a linking area having an recess in the downstream direction, such that said radially inner end of the leading edge of the blade is located further downstream than the upstream end of the root.

Description

AUBE A BECQUET

The invention relates to a blade for a turbomachine, such as in particular an airplane turbojet or turboprop, and to a fan rotor and a turbomachine thus provided.

Typically, a turbomachine rotor comprises a disc carrying at its outer periphery blades having portions forming aerodynamic blades and feet engaged in grooves of the outer periphery of the disc. These grooves are substantially axial (that is to say substantially parallel to the axis of rotation of the rotor) and arranged circumferentially alternately with teeth of the disc. The vanes are held radially on the disc by cooperation of shapes of their feet with the grooves, and thus the teeth, of the disk, the blade roots being for example of the dovetail type.

Once the blade is in place in the corresponding groove of the disk, it is known to interpose a shim between the root of each blade and the bottom of the groove, to immobilize the blade in this groove radially. Typically, each wedge comprises at its upstream end a spoiler which extends radially outwards and which has a downstream radial face forming an axial support of a radial face upstream of the blade root, to retain the blade axially towards the upstream. Due to the significant shear forces in the axial direction during the transmission of certain forces, it has been proposed to over-dimension the spoiler in the axial direction so that it can withstand these forces, which results in a significant axial space requirement. each spoiler, and an increase in the rotor mass of the blower.

To compensate for the oversizing in the axial direction of the spoiler of a wedge, it is possible to trim all the upstream end of the corresponding blade root. However, this solution is not satisfactory because in this case the blade root has an axial dimension shorter than that of the groove of the disk and comes to exert forces of important contact in the side walls of the groove which can cause premature wear thereof.

The problem arises in particular on a fan rotor, it is in this context that WO2009 / 144401 has presented a solution for reducing the shear forces applied to the spoiler of the hold, in particular in case of loss of a blower dawn.

This solution provides that the spoiler of each shim has a downstream abutment face on which the upstream end of the blade root rests in the event of violent force, this downstream abutment face being oblique with respect to the axis of rotation of the rotor.

Thus, in this combination of wedges and blades, the blades are intended to work more than before and we do not reduce the constraints in them. The flow of the stresses is not distributed between the wedge and the dawn. In other words, in the distribution of the constraint flow generated by the blade, the solution of WO2009 / 144401 is a series assembly where the flow of stresses passes through the dawn then by the wedge, with high stresses in the dawn .

Moreover, US201 1/0076148 proposes, on a turbomachine blade, to conform in particular manner including the inter-blade inner platform which is located radially between the foot and the blade. But this imposes precisely constraints of form which can be limiting.

Without resorting to these options, the object of the invention is notably to provide a simple, effective and economical solution to the aforementioned drawback, thanks to an upstream and / or downstream protrusion of the blade roots which increases the axial span length. .

It more specifically proposes a turbomachine blade, or a set of vanes / platforms where each blade has an upstream side and a downstream side and has, in a radial direction of elongation of the blade: a blade having a leading edge along the upstream side and a trailing edge along the downstream side, and a foot to engage in a groove of a disk of the turbomachine, the foot being located radially further inwards than the blade and having upstream and downstream ends, transversely to said radial extension direction, a platform inter-blade interior (belonging or not to the blade) extending further radially between the foot and the blade, so as to define the radially inner limit of the vein reserved for the flow of gas to be circulated in the turbomachine,

characterized in that, on each blade, at least one of the upstream and downstream ends of the foot is connected to a radially inner end of the leading edge, respectively of the trailing edge, of the blade by the upstream edge, respectively the downstream edge, a radially intermediate connection zone (or stilt) between the foot and the interaubes inner platform, and having a recess downstream, respectively upstream, so that said radially inner end of the edge of attack, respectively of the trailing edge, of the blade is located further downstream, respectively upstream, than the upstream end, downstream respectively, of the foot.

By this or these recess (s), a limitation of the mass of blades, critical point on such rotating assemblies, is targeted.

In addition, by such an upstream and / or downstream increased range, the intention is to work the front (upstream) and / or the rear of the blade root and thus to distribute the flow of constraints on a larger area, correspondingly decreasing the mean and local stress.

By thus axially increasing the length of the foot span, the stress flow will be distributed in this spoiler and in the rest of the range, downstream.

It is no longer a serial assembly as in WO2009 / 144401, but a parallel assembly; so we reduce the local constraints.

For all purposes, it is stated that, on a fan blade, the range is the area of the blade root which is in contact with the teeth of the disk which receives it, while the foot is engaged in the groove of this disc. The axial span length of the blade root is therefore, parallel to the axis of rotation of the rotor or perpendicular to the radial direction of elongation of the blade, the length according to which the foot is in lateral contact with the teeth. of the disc. The stub zone of a blade being conventionally the zone located radially between the radially inner end of the blade - where the inner platforms are arranged - and the foot, therefore inwardly with respect to the radially inner limit that defines these inner platforms for a gas flow flow to circulate in the turbomachine, this will participate in the reduction of stresses in the stilt, upstream side.

By conforming this stilt zone with an upstream edge, respectively downstream, of concave shape advancing upstream, respectively moving downstream, from the foot to the blade, it will be moreover not only transit the flow of stress by a important section to reduce the local stress in the stilt, but it will also allow the flow of constraints to diffuse as much as possible through the upstream contact zone.

Giving a radiating shape (with a radius) to the concave shape of the connection, along the upstream edge, respectively downstream, of the stilt zone, between the inner platforms and the foot, will further promote, by its rounding, the above-mentioned diffusion of the flow of constraints.

Note that an axial reach of the elongate foot upstream, respectively the downstream, will be all the more useful if, radially outwardly beyond a concave first shape, the leading edge, respectively leakage, the blade has a convex shape, which, with respect to a straight line parallel to the radial direction of elongation of the blade and passing through the upstream end of the foot, advances upstream, respectively backward downstream, from this line.

If, as recommended, said convex blade shape is more ventrous at the leading edge than at the trailing edge (L4> L5 below), the center of gravity the dawn (at least in its pale part) will be a priori closer to the leading edge than the trailing edge. The axial reach of the elongated foot will participate in the stability of the blade and naturally prevent its weight causes it to swing upstream at a stop and rather to the rear (downstream) during the rotation of the fan.

Moreover, to optimize both the desired mechanical effect and the weight of the blade, it may be preferable that the blade has:

a bearing which, along said radial direction of elongation of the blade, flares towards a free end (radially inner),

with, along this direction, a distance (R) between the birth of the bearing and the free end,

and, perpendicularly to said radial elongation direction, a distance (L) between the upstream end of the foot and either said radially inner end of the leading edge of the blade, or the downstream end of said strike of the zone of connection between the blade and the foot,

- with L less than or equal to 2R. As to the fact of providing, always on the upstream side, the leading edge of the blade is connected at its radially inner end by a concave shape, this will prevent a forward upwardly pronounced foot, or to favor certain aerodynamic aspects.

By providing, moreover:

- that the foot of one (of each) blade has radially inward, an axial end edge parallel to the axis of the groove of the disc which receives it, and

that on the upstream side, the upstream end of the foot defines an upstream end face which is perpendicular to the axis along which said axial end edge of the foot extends,

we will provide a frontal support, front, at the upstream end of this foot.

To further promote the limitation of mase blades, it is also proposed that the upstream end respectively downstream of the foot is connected radially to the outer edge upstream, respectively downstream of a radially inner portion of said connection zone between the foot and the inter-blade inner platform, by said recess downstream, respectively upstream, so that, transversely to said radial direction, the upstream end respectively downstream of the foot is located further upstream respectively downstream than said upstream edge, respectively downstream of said connecting zone, along its entire length.

If necessary, the invention will be better understood and other details, characteristics and advantages thereof will appear even more clearly on reading the following description given by way of non-limiting example and with reference to the accompanying drawings. wherein :

- Figure 1 is a partial schematic view in axial section (except the blade which is seen from the side) of a fan rotor of a turbomachine according to the prior art,

FIG. 2 is a partial schematic side view of a fan rotor blade of a turbomachine according to the present invention,

FIG. 3 is a diagrammatic view on a larger scale of part of FIG. 2,

FIG. 4 is a partial side schematic of a blade alternative according to the present invention,

FIG. 5 is a partial diagrammatic view in axial section (except the blade which is seen from the side) of a fan rotor provided with vanes each like that of FIG. 4,

FIG. 6 is a local section along the line VI-VI of FIG. 3 and

- Figures 7,8 schematically two types of blades and two assemblies possible.

In connection with Figure 1, the blades 12, of which only one is shown, correspond to a solution of the prior art. Thus, the blade 12 'of FIGS. 2, 3 could be substituted for each blade 12 and the other parts presented of the rotor could be reused in order to implement the invention. On the fan rotor 100, the vanes 12 are carried by a disc 14 and between these vanes are interspersed with the interaubes platforms 16. The disc 14 is fixed to the upstream end of a shaft not shown of the turbomachine.

In this case, the inter-blade platforms 16, which are circumferentially disposed (about the axis A), end to end with inner platforms of adjacent blades, so that they together define a radially inner and circumferential limit for a gas flow stream (vein 21) to be circulated in the turbomachine, are each one-piece with the rest of the blade (blade, stilt and foot) which carries them; however, it could be reported platforms extending laterally to the immediate vicinity of each side face, such as 12a.

Each fan blade 12 comprises a blade 13 connected at its radially inner end to a foot 18 which is engaged in a substantially axial groove 20 of complementary shape of the disk 14 for retaining radially this blade on the disk.

The expressions :

radial and axial refer respectively to the direction of elongation of the blade and to the orientation of the groove where the foot 18 is engaged (parallel to the axis A of rotation of the rotor), it being specified that the foot has (radially inwardly) an inner end edge 19 axial (or radially inner free end) to engage parallel to the axis of the groove 20,

- Inside and outside (see respectively EXT and INT Figures 1, 2) refer to the position along the direction of elongation of the blade; the foot 18 is inward, the blade 13 more outwards,

- upstream and downstream (see respectively AM and AV Figures 1 -3) refer to the position along the axial direction A,

Thus, on the rotor, the feet 18 are engaged axially and retained radially in grooves, or cells, of the outer periphery of the rotor. disc, these grooves being arranged alternately with teeth of the disc.

A wedge 22 is interposed between the foot 18 of each blade and the bottom of the corresponding groove 20 of the disk to radially immobilize the blade in the groove. Each wedge 22 is formed of an elongate bar carrying at its upstream end a spoiler 24 which extends radially outwardly.

The spoiler 24 is, in the mounting position shown in Figure 1, axially supported on a radial face 26 of the upstream end of the blade root 18 to retain the blade axially upstream on the disk 14.

An annular flange 28 is fixed coaxially on the upstream end of the disc, 14, the outer periphery of this flange 28 extending upstream of the spoilers of the wedges 22. The flange 28 is retained on the disc 14 by dog teeth 29 , 31, the flange 28 further comprising at its inner periphery an annular flange 30 which is interposed between an upstream annular flange 32 of the disc 14 and an inner annular flange 34 of a cover 36 arranged upstream of the disc 14 and the blades 1 2. The flanges 30, 32 and 34 comprise axial screw holes 37 or the like for clamping the flanges together. Towards its radially inner end, the radial face 26 of the foot 18 is chamfered and therefore comprises an oblique upstream end face 39 provided to bear against a substantially parallel oblique face 41 of the spoiler 24 of the wedge, particularly in case loss or rupture of one of the fan blades 12.

The face 39, which extends obliquely with respect to the axis A of the fan, thus connects the upstream radial face 26 of the foot 18 to its radially inner axial edge 19.

As appropriate as it is, this embodiment provides a solution especially in case of loss or breakage of dawn. However, the invention aims first of all to take into account the management of stress flows in current operational operation, normal, therefore without loss of blade, when these stress flows are generally along the axis 10, and directed from the dawn to the disk. The aim is to reduce them, especially in the connection zone between the blade and the foot.

It is especially for this purpose that the solutions of FIGS. 2 to 4 propose, in accordance with the invention, a blade 12 ', respectively 12 ", in which the upstream end 450', respectively 450", of the foot 18 ', respectively 18 ", is connected to a radially inner end 430 ', respectively 430", of the leading edge of the blade 13', respectively 13 ", by the upstream edge of a connecting zone having a recess downstream 49 ', 49 ", so that said radially inner end of the leading edge 431', respectively 431", of the blade is located further downstream than the upstream end (450 ', 450 ") of the foot.

Thus, when, as FIG. 5, the blade is engaged in the groove 58 of the disk 56, an over-length L of span forming a spoiler, or an outgrowth, is available axially (parallel to the axis A) for the distribution of stress flows, in particular rotor in normal operation.

For the explanation of the subject, L2 marks, in FIGS. 3 to 5, the length of range of the blade, ie the length which, perpendicularly to the elongation direction 10, and parallel to the axis A, s' extends between the upstream and downstream ends (respectively 450 "and 451" 4) of the blade root considered, this foot being, over the entire length and once mounted, contained inside the groove 58 of the disk 56 as illustrated Figure 5 for the dawn 12 '.

Hereinafter, reference is made to the solution of FIGS. 2,3, but that of FIG. 4 is also concerned. It suffices to replace the premium (') by the double premium (") .Accurately, along the axis A, the upstream end 450' of the spoiler is located more upstream than the end is upstream 160 'of the inner lateral platforms 16', this upstream end 160 'corresponding to that of the stilt zone 47' at the location of its upstream connection with the base of the blade, in the event of 16 'forms reported. It will be understood that this upstream position is assessed along the axis A of rotation of the rotor, or parallel to the rectilinear axial end edge 19 'that, as previously, the foot 18' of the blade 12 'presents (radially inwards) and which is to engage in the axial groove of the disc concerned.

What was planned above upstream could be downstream, or upstream and downstream to further lengthen L2 reach.

Thus, for the downstream, is it provided in the same figures that the downstream end 451 ', 451 "of the foot is connected to a radially inner end of the trailing edge 457', 457" of the blade by the downstream edge of a connecting zone (or staggered 47 ', 47 ") radially intermediate between the foot and the inter-blade inner platform 16', 16" (whether integral or not with the blade), in having an upward recess 490 ', 490 ", such that said radially inner end of said trailing edge (432' figure 2) of the blade is located further upstream than the downstream end of the foot (451 'figure 2 ).

By causing the flow of stresses to pass through an important section, the local stress in the stilt will be reduced.

In this regard, to facilitate the diffusion of the aforementioned forces to the end (upstream, AM) of the scope, Figures 2 and 3 show the advantage of providing that the stilt zone 47 'located radially between the platforms 16 'and the foot 18' (thus internally with respect to the airstream defined by these platforms, once the blade 12 'mounted), is connected to the foot at its upstream edge by a concave shape given at step 49 'or 49 ".

Predicting that such a concave shape is radiating (defined by a radius) will further facilitate the diffusion of efforts, avoiding angles.

For a good axial support, it is recommended that at the most upstream end, the foot has an upstream end face 450 'oriented perpendicular to the axis along which extends the axial end edge 19 '.

In addition, to promote the balance of the blades, it is recommended that upstream and downstream, the most ventrous areas of the blade respectively at the leading edge and the trailing edge (453 ', 453 " and 459 ', 459 ", respectively; FIGS. 2, 4) are located respectively upstream and downstream of said respectively upstream and downstream ends of the foot: axial distance L4 and L5 FIG.

For overall balance, it is recommended that L4> L5.

And to further limit the mass of the blades, the downstream end 451 ', 451 "of the foot will connect favorably radially externally to the downstream edge 491', 491" of the radially inner portion of the stilt zone 47 ' , 47 "by an offset upstream 490 ', 490".

Thus, transversely to said radial direction 10 of the blade, here along the axis A, the downstream end 451 ', 451 "of the foot will be situated further downstream than said downstream edge 491', 491" to which this downstream end connects.

Again for the general balancing of the blade and efficient guidance of the air flow by the inner platforms, such as 16 ', 16 ", it is even proposed that the downstream end 161', 161" of each of these platforms is located further downstream than said downstream end of the foot, along the axis A, therefore transversely to said radial elongation direction 10 of the blade concerned (see distance L3, Figure 5).

FIG. 7 shows the arrangement of the platforms 16 'of the blades 12' whose feet 18 'are held about the axis A in a circumferential groove 58 "of the disc 56', each platform 16 ', integral with the blade, extends essentially in the axial and circumferential direction, all around the blade, transversely to the axis 10. A spoke 59 defines a connecting portion between the blade 13 'and the platform 16' concerned, having a face progressive transition with a concave profile, thus mounted, the platforms abut one against the other two by two by their circumferential end face 160 '.

Figure 4, the dawn is without a single-piece inner platform. Each inner platform (one of which 16 "a is shown by transparency) is attached, arranged laterally between two circumferentially successive blades and fixed to the disk so that the vein 21 is still internally restricted.

Thus, in this version, there is, on the dawn, radially, a direct connection between the stilt 47 "and the blade.

Figure 8, we see better than the platforms are reported: that schematically 16 "extends circumferentially between a pair of blades 12", of which only one is represented, with its foot 18 "retained in one of grooves 58 of the disk 56 formed between two circumferentially successive ribs 140 around the axis A.

This does not prevent that the leading edge 431 "of the blade is connected to its radially inner end 430" by a concave shape 433 ".

3, this is even clearer: the corresponding concave shape 433 'is even recessed downstream with respect to the axial position of the concave shape 49' that presents the upstream edge of the connection zone between the blade and the foot (axial distance L1).

In this respect, and whether it is a blade with an integrated inner platform or not, it will therefore be advantageous (especially for mass, but also for balancing, if the shapes created are different upstream and downstream), that upstream and / or downstream, the upstream end, downstream respectively, of the foot is connected, radially external to the upstream edge, respectively downstream, of a radially inner portion of said zone 47 ', 47 "of connection between the foot and the inter-blade inner platform (16' or 16"), by said recess downstream, respectively upstream, so that, transversely to said radial direction 10, the upstream end, respectively downstream, of the foot is located further upstream, respectively more downstream, that said upstream edge, downstream respectively, of said connecting zone, this (radially) over its entire length of this zone (thus from the connection to the foot to the level of the inner platform).

Another common point between the illustrated versions: radially outwardly (axis 10) and beyond the concave shape 433 ', 433 ", the leading edge 431', 431" of the blade has a convex shape 435 ' , 435 ".

This is most clearly seen in Figure 2.

On the other hand, in the version of FIG. 4 with no integrated platform, the "concave form 461", which is preferably present in the integrated platform version (FIG. radially inner end of the trailing edge of the blade with the platform Radially, between the platform 16 "a and the zone 459" the largest (downstream) of the blade at the trailing edge, the shape of this edge of escape remains despite all concave overall

Combining these successively concave and then convex forms along the leading edge of the blade, with a connection to the downstream recess (49 ', 49 ") of the concave shape (433', 433"), will be able to finely manage the balance to be found between the over-length L axial range (parallel to the axis A), the axial position of the center of gravity of the blade (important in particular for its static and dynamic equilibrium, rotating rotor) and the aerodynamic performance requirements.

Figures 3 and 6 in particular, it will be noted that in connection with this point, it is advisable:

that, along said radial direction 10 of elongation of the blade concerned, its bearing area flares towards a free end, such as FIG. 3,

with, in this direction, a distance R between the birth of the span (180 ', 180 "FIGS. 3,4) and the free end (19' or 19"),

and, perpendicularly to said radial elongation direction, a distance L between the upstream end of the foot and either said radially inner end (455 ', 455 "FIGS. 2, 4) of the leading edge of the blade, either the downstream end of the recess (49 ', 49 ") of the said zone of connection between the blade and the foot (see FIG. 3),

where L is less than or equal to 2R.

The same consideration and therefore the respect of the above ratio can usefully be provided downstream, with then L'inferior or equal to 2R '. The dimension R '(height of the downstream foot, along the axis 10) will be (fig.3) or not (see fig.2) equal to R. A height R'> R will favor a favorable back stop of the foot as shown schematically in Figure 5.

Both the blades 12 ', 12 "could be installed on the rotor 100' shown in Figure 5.

The disk 56 is arranged around the axis A of the turbomachine, and is rotated by a downstream drive shaft (not shown).

Blades, including that 12 'already presented, between which inter-platforms inter-blades 16' are inserted, are carried by the disk 56.

The foot 18 'of each blade is engaged in a substantially axial groove 58 of the disk 56, formed between two teeth or ribs 140 of the disk, and for retaining radially this blade on the disk 56.

The rotor 100 'is furthermore equipped with axial retaining means upstream of the blades on the disk. These comprise a flange 74 mounted in the annular groove of the disk 56 and forming an axial support of the blade roots. The flange 74 is immobilized in rotation by means of a ring 86 having a cylindrical portion delimited by internal and external cylindrical faces. The cylindrical portion of the ring bears axially from the outside against a flange 66 of the disc. The flange 66 comprises, regularly distributed over its entire circumference, axial screw holes 70. The flange 74 is immobilized in rotation by abutment of its solid parts against projections of the ring. A cover 96, for example aluminum and conical, is fixed on the disc. The fan blades 12 'are retained axially in the grooves 58 of the disc 56 via means 70, 74, 86, 96 above arranged upstream of the blades.

A shim 142 is interposed between the root 18 'of each blade and the bottom of the corresponding groove 58 of the disk 56 to immobilize the blade on the disk 56 radially.

The platforms 16 'inter-blades always form a wall which delimits internally the vein 144 of the air flow entering the turbomachine, and comprises means which cooperate with corresponding means provided on the disc 56, between the grooves 58, to fix the platforms on the disk.

The low pressure compressor, BP, 150 is here arranged downstream of the fan disc 56 and directly in abutment against the downstream ends of the feet 18 'of blades and ribs 140 of the disc. There is therefore no constraint of radial depth of the ribs related to the engagement of downstream hooks. The axial support of the compressor BP 150 is here realized by a radial tab 151 of the upstream end of the upstream annular arm 153 of a downstream labyrinth ring. Axially fastened, typically bolted, 155, may complete the support above, radially just outside, between the radial tab 151 and the stilt zone, here 47 '(see Figure 5).

The profile of the inner wall 152 of the disc 56 may be frustoconical flaring downstream.

Claims

1. A blade for a turbomachine, the blade (12 ', 12') having an upstream side and a downstream side and having in a radial direction (10) of elongation of the blade:

a blade (13 ', 13 ") having a leading edge along the upstream side and a trailing edge along the downstream side,

- a foot (18 ', 18 ") to engage in a groove of a disk of the turbomachine, the foot being located radially further inwards than the blade and having upstream and downstream ends, transversely to said radial direction ( 10) elongation,

an inter-blade inner platform (16) located radially between the foot (18 ', 18 ") and the blade (13', 13"),

characterized in that at least one of the upstream (450 ', 450 ") and downstream (451', 451") ends of the foot is connected to a radially inner end of the leading edge (431 ', 431 "), respectively of the trailing edge (457 ', 457 "), the blade by the upstream edge, respectively the downstream edge, of a connecting zone (47', 47") radially intermediate the foot (18 ', 18 ") ) and the inter-blade inner platform (16), and having a downstream recess (49 ', 49 "), respectively upstream (490', 490"), so that said radially inner end (430 ', 430' ') of the leading edge, respectively the trailing edge (432', 432 "), of the blade is located further downstream, respectively upstream, than the upstream end, downstream respectively, of the foot.

2. blade according to claim 1, wherein the upstream edge, respectively downstream of said zone (47 ', 47 ") of connection has a concave shape and / or which advances upstream, backs downstream, since the blade to the foot.

3. blade according to claim 1 or 2, wherein the upstream edge of the zone (47 ', 47 ") connecting the blade and the foot has a shape that has a radius.

4. blade according to one of claims 1 to 3, wherein the leading edge (431 ', 431 "), respectively of the trailing edge (457', 457"), the blade is connected at its end radially; interior by a concave shape (433 ', 433 ").

The blade according to claim 4, wherein radially outwardly and beyond the concave shape (433 ', 433 ") the leading edge (431', 431"), respectively of the trailing edge (457 ', 457' '), the blade has a convex shape.

6. blade according to claim 5, wherein the convex shape of the leading edge (453 ', 453 ") of the leading edge is more ventrue than that

(459 ', 459 ") from the trailing edge.

7. blade according to one of claims 1 to 6 having:

a span (180 ', 180 ") which, along said radial direction (10) of elongation of the blade, flares towards a free end (19'),

with, along this direction, a distance (R) between the birth of the span (180 ', 180 ") and the free end (19'),

and, perpendicular to said elongate radial direction (10), a distance (L) between the upstream end (450 ', 450 ") of the foot (18', 18") and either said radially inner end (430 ' , 430 ") of the leading edge of the blade, ie the downstream end of the recess (49 ', 49") of said connection zone between the blade (13', 13 ") and the foot (18 ', 18') ")

- with L less than or equal to 2R.

8. blade according to one of the preceding claims, characterized in that the upstream end, respectively downstream (451 ', 451 ") of the foot is connected, radially outer, to the upstream edge, respectively downstream (491', 491 ") of a radially inner portion of said connecting zone (47 ', 47") between the foot (18', 18 ") and the inter-blade inner platform (16), by said downward recess (49). ', 49''), respectively the upstream (490', 490 '') so that, transverse to said radial direction (10), the upstream end, respectively downstream of the foot is located further upstream, respectively downstream of said upstream edge, respectively downstream (491 ', 491 ") of said zone (47', 47") of connection, over its entire length.

9. Set comprising:

turbomachine blades, each blade (12 ') having an upstream side and a downstream side and having, in a radial direction (10) of elongation of the blade:

a blade (13 ") having a leading edge along the upstream side and a trailing edge along the downstream side,

- and a foot (18 ") to engage in a groove of a disk of the turbomachine, the foot being located radially further inside than the blade and having an upstream end,

inner inter-blade platforms (16 "a) interposed each between two successive blades, radially opposite an intermediate level between the foot (18") and the blade (13 ") of these blades,

characterized in that, on each blade, at least one of the upstream (450 ") and downstream (451") ends of the foot connects to a radially inner end of the leading edge (431 "), respectively of the leading edge. leakage (457 "), of the blade by the upstream edge, respectively the downstream edge, of a connecting zone (47") radially intermediate between the foot (18 ") and the inner platform inter-blades (16" a) , and having a recess downstream (49 "), respectively upstream (490"), so that said radially inner end of the leading edge, respectively the trailing edge, of the blade is located more downstream, respectively upstream, than the upstream end, downstream respectively, of the foot.

10. A fan rotor for a turbomachine, the rotor comprising a disk (14, 56) having an axis of rotation and having at the outer periphery substantially axial grooves (20, 58) in which are arranged feet (18 ', 18 "). of blades, each of these vanes being according to one of claims 1 to 8 or according to the assembly of claim 9.

1 1. A rotor according to claim 10, wherein each inner platform (16 ', 16 "a) has an upstream end and extends laterally from other than a blade, so that the platforms together define a radially inner limit for a flow (21, 144) of gas flow to be circulated in the turbomachine, the upstream end (450 ' , 450 ") of the foot of each blade being located further upstream than is the upstream end (160 ') of each inner platform.

Rotor according to Claim 10 or 11, in which:

- the root of a blade has radially inward, an axial end edge (19 ', 19 ") parallel to the axis of the groove (20,58) which receives it, and

- On the upstream side, the upstream end (450 ', 450 ") of the foot defines an upstream end face which is perpendicular to the axis along which extends said axial end edge of the foot.

13. A turbomachine, such as a jet engine or an airplane turboprop, characterized in that it comprises several blades according to one of claims 1 to 8, or the assembly of claim 8 or the fan rotor (100,100 ') according to one of claims 10 to 12.